[Milsurplus] RCH Receiver

[WA5CAB at cs.com]

No.  Your point could be valid if the RCH were like the Command Set receivers 
which have no audio gain control.  But look at the RCH schematic.  Box stock 
audio circuit for almost all WW-II ground and shipboard receivers except that 
some separate the audio and RF gain pots (like the TCS).  The audio gain pot 
sits between the output of the 6H6-GT detector and ground.  The wiper goes to 
the grid of the 6SQ7-GT first audio.  The cathode of the 6SQ7 goes to ground 
through a resistor.  No sort of feedback or other connection to anywhere else in 
the circuit.  With the audio gain pot fully CCW, it wouldn't matter what the 
condition of the capacitor across the cathode resistor was.  No input equals 
no output.  The only way in which there could be input would be for the grid 
not to be grounded with the pot fully CCW.

In a message dated 2/21/2008 10:27:51 PM Central Standard Time, 
jmccarty at alcatel-lucent.com writes: 
> Maybe one of the caps didn't reform as well as hoped. I had this happen on 
> an
> ARC-5. You couldn't build up enough voltage to bias the cathodes to turn 
> down
> the gain.
> 
> 
> 73
> 
> 
> n9hrt
> 
> On 2/21/2008 5:52 PM, WA5CAB at cs.com wrote:
> >Bob,
> >
> >According to the manual, it was primarily intended as an entertainment
> >receiver but good enough to be a backup for the communications receivers
> >aboard (at least when it was new).
> >
> >It's been 39-1/2 years but I don't recall not being able to turn the
> >volume all the way down on the one we had aboard.  I just took a quick
> >look at the schematic.  Check the audio gain pot.  My guess is that
> >you've lost the ground connection at the bottom.
> >
> >In a message dated 2/21/2008 5:19:49 PM Central Standard Time,
> >w9ran at oneradio.net writes:
> >
> >>I picked up this RCH from a buddy who used to collect Navy stuff, but he
> >>said he'd never had it powered up.  It incubated in my garage until I
> >>got around to lugging the 69 pounds (of 109 total) chassis down to the
> >>bench, but to my surprise the caps reformed nicely and it came up
> >>working like a champ.  It's an 11 tube superhet built by EH Scott, for
> >>Navships and based on the blank "placed in service" nameplate I'm
> >>guessing this one may have spent its career in a warehouse.
> >>
> >>What was the RCH used for?  I know Scott made "entertainment" receivers
> >>that could operate from AC or DC mains but the RCH is a really heavy,
> >>very ruggedly constructed set with a 120VAC power supply and BFO.  
> >>Since it has both LF and HF coverage, skipping the BC band I'm assuming
> >>it was a communications receiver,  but the geared flywheel tuning sure
> >>makes it a great SWL band-scanner.   And it's hot from the longwave
> >>beacon band all the way up to the 17meter shortwave band.
> >>
> >>Another question - the "Gain" control is a ganged pot that adjusts RF/IF
> >>and Audio gain, but even at minimum position audio is still quite loud. 
> >>Was this by intent?
> 

Robert & Susan Downs - Houston
<http://www.wa5cab.com> (Web Store)
MVPA 9480
<wa5cab at cs.com> (Primary email)
<wa5cab at comcast.net> (Backup email)
   
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